Does the concept of eternity have any meaning at all? It’s a very philosophically nebulous thing when taken beyond a superficial level. We can’t fathom existing for a huge number of years anymore than we can conceive being the size of the universe. Spiritually being eternally cast into fire could mean to be removed from the being that is everything which is to be nothing forevermore. Or eternity can just mean until the end of time, which could very well be finite.